linux-kernel - Re: [PATCH RFC 0/2] rtc-cmos: Workaround unwanted interrupt generation

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Message-ID: <20160719142907.GG7132@piout.net>
Date:	Tue, 19 Jul 2016 16:29:07 +0200
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Pratyush Anand <panand@...hat.com>
Cc:	Alessandro Zummo <a.zummo@...ertech.it>,
	rtc-linux@...glegroups.com,
	open list <linux-kernel@...r.kernel.org>,
	Prarit Bhargava <prarit@...hat.com>,
	RuiRui Yang <dyoung@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>, mingo@...nel.org
Subject: Re: [PATCH RFC 0/2] rtc-cmos: Workaround unwanted interrupt
 generation

Hi,

On 18/07/2016 at 17:17:44 +0530, Pratyush Anand wrote :
> Hi RTC-Maintainers,
> 
> 
> On Mon, Jul 4, 2016 at 9:49 PM, Pratyush Anand <panand@...hat.com> wrote:
> > On 27/06/2016:10:19:07 AM, Pratyush Anand wrote:
> >> On 21/06/2016:10:25:34 AM, Pratyush Anand wrote:
> >> > We have observed on few machines with rtc-cmos device that
> >> > hpet_rtc_interrupt() is called before cmos_do_probe() could call
> >> > hpet_rtc_timer_init(). It has not been observed during normal boot/reboot
> >> > of machines. It *sometime* happens when system is booted with kdump
> >> > secondary kernel. So, neither hpet_default_delta nor hpet_t1_cmp is
> >> > initialized by the time interrupt is raised in the given situation.
> >> > Therefore while loop of hpet_cnt_ahead() in hpet_rtc_timer_reinit() never
> >> > completes. This leads to "NMI watchdog: Watchdog detected hard LOCKUP on
> >> > cpu 0".
> >> >
> >> > I am still clueless, how can an interrupt be raised before RTC is enabled.
> >> > But i do not have any idea about this device, so I am putting this patch as
> >> > RFC to get feedback from hpet/rtc-cmos developer. I am sure there would be
> >> > some better solution than this.
> >>
> >> Do you think that if I improve commit log of patches as pointed by Thomas and
> >> send a formal version of these patches, then they should acceptable to upstream?
> >
> > A gentle reminder for your comment/feedback :-)
> 
> Please let me know how to make progress on this. If you think, there
> could be some better way to handle this issue then please let me know.
> If you need any more data then also please let me know.
> 

Well, the change is x86 specific and I don't know much about HPET so
until you get an ack from the x86 maintainers, I guess I can't help
much.

-- 
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com